Such seals, sometimes referred to as self-locking seals, typically comprise a body generally molded thermoplastic which has a female socket therein having a recess. A strap is attached to the body and has at its free end typically a pair of tangs, which being molded thermoplastic, are somewhat resilient. The tangs are inserted into the socket in interference fit so that the tangs are compressed during insertion. Once the tangs are inserted into the socket cavity which is enlarged relative to the egress of the cavity, they expand inside the cavity. Once the tangs expand inside the cavity, they engage with shoulders formed by the cavity egress precluding removal from the socket. For example, in U.S. Pat. No. 3,367,701 such a seal is illustrated. Also as illustrated in this patent is an abutment which is located within the cavity for spreading the tangs apart so as to preclude reverse removal of the tangs once inserted and locked into the recess. Other self-locking security seals are disclosed in U.S. Pat. Nos. 4,106,801; 4,818,002; 4,175,782; 5,118,148; and 3,149,869. Several of the above patents disclose an arrangement in which a set of tangs are attached to one end of a strap and a body including a socket is attached to another end of the strap, the entire arrangement being molded thermoplastic. The tang arrangement is inserted and locked to a cavity in the socket.
The present inventor recognizes a need for an approved seal employing a locking arrangement such as disclosed in the aforementioned patents. One problem recognized is that it is desirable to provide tamper evidence when a lock has been broken into and the seal has been somewhat reassembled to hide the fact that the seal has been broken into. For example, in all of the seals disclosed above if a strap portion is broken and the tangs removed, it would be difficult to visually identify that the tangs are still locked in place in the arrangement if the strap is reinserted into the socket and glued in place without the tangs intact. A second problem is that in many cases the seals are employed in the transportation industry where the seals are used to lock doors of trucks and the like using the hasps of the truck doors holding the cargo. The driver of the truck needs to carry extra seals so that on the return trip the driver can reseal the truck doors after the truck has been unloaded and reloaded at a first destination. The present inventor recognizes a desirability of reducing the number of extra seals that a driver has to carry in order to provide a locking seal for the driver after a seal has been used and broken open to permit unloading of cargo and, thus, requiring a second new seal for resealing any cargo.
Another problem recognized is that sometimes the tang and socket arrangements at either end of a strap are relatively large and cannot pass through relatively small openings. A need is seen for providing a thermoplastic seal of the type described which can be used with relatively small openings employing the structure comprising tangs and a mating socket. Further, a need is seen for providing a seal which comprises an integral structure so that all of the components are joined and can not be lost with respect to one another during use. Another problem recognized with prior art seals is tampering. It is desirable to provide a pick-proof seal. The present inventor recognizes that a pick which can be inserted in the socket may be utilized to flex the mating locking tang to a point where it can be removed. A need is seen for a solution to the above problems.